This paper’s main goal is to advance some considerations on the interrelations between port cities and capital. More specifically, it sheds light on how these interdependencies took place in the eighteenth-century Portuguese and Spanish Atlantic world. This paper thus seeks to draw an urban political economy in transimperial, global, and contractual perspectives. For so doing, particular attention will be put to Rio de Janeiro’s projection far beyond the South Atlantic, and in particular, its interconnections with the Rio de la Plata basin and Potosi markets. Attention will also be paid to the impact of and repercussions that far-flung economic phenomena had for the urban domestic markets.